Maximum Capability Research Articles

Polyethylenimine functionalized graphene oxide and cellulose nanofibril composite hydrogels: Synthesis, characterization and water pollutants adsorption

A stable 2,2,6,6-tetramethylpiperidine-1-yl)oxyl (TEMPO)-oxidized cellulose nanofibril (TCNF)/graphene oxide (GO)/polyethylenimine (PEI) composite hydrogel was synthesized by self-assembly instead of chemical crosslinking. Their chemical, morphology, surface, and mechanical properties were characterized and adsorption behavior for methyl blue (–) was systematically investigated in terms of the optimal GO content, pH effect, kinetics, and isotherm models. Additionally, to assess the adsorption capability of the TCNF/GO/PEI hydrogel for various contaminants, its effectiveness was also tested for methylene blue (+), Cu (II), and soybean oils. The maximum adsorption capability for the methyl blue (−) dyes increased from 3125 to 3962 mg/g when 13.3 % of GO was added. The adsorption capability for Cu (II) and soybean oils rose from 205.3 to 218.5 and 2.1 to 7.2 mg/g, respectively. The adsorption capability of optimized TCNF/GO/PEI hydrogel for a variety of contaminants was improved overall based on the increase of surface area, electrostatic interactions, and hydrophobic domains. Moreover, adding GO did not impact the adsorption mechanism but increased the external diffusion rate in the intraparticle diffusion model. This work provides a self-assembling route to TCNF/GO/PEI hydrogels with great potential for the removal of multiple water pollutants.

Power distribution system restoration based on soft open points and islanding by distributed generations

Abstract A powerful and efficient program for restoring the electrical distribution system by effectively utilizing the maximum capabilities within the system, including soft open points, distributed generation resources, and network configuration changes, can significantly reduce both the quantity and duration of lost loads caused by permanent faults. In this research study, we address the issue of distribution network restoration with a focus on soft open points (SOPs) and intentional islanding using distributed generations. This problem is formulated as a constrained optimization problem in order to determine the optimal distribution network configuration, quality of intentional islanding through DGs, control function of SOPs, and amount of load shedding. The objective is to minimize lost load while minimizing switching operations and preferably minimal islanding. Given that this problem involves multiple complexities such as combinatorial nature, mixed-integer variables, non-linearity, non-convexity along with numerous variables and constraints; we employ an evolutionary method known as simulated annealing (SA) algorithm to solve it without any simplifications or assumptions about convexity. To enhance efficiency during implementation of SA algorithm, Kruskal’s algorithm is utilized for generating radial solutions which restricts search space to feasible solutions resulting in quicker attainment of high-quality optimal solutions. Finally, the outcomes of implementing the suggested approach on the 69-bus IEEE distribution system are presented and examined. It is demonstrated that by leveraging the potential of soft open points in load transfer control and network voltage regulation, along with utilizing intentional islanding capability provided by distributed generation resources, the restoration capability of the distribution system can be greatly enhanced.

Waste biomass-based graphene oxide decorated with ternary metal oxide (MnO-NiO-ZnO) composite for adsorption of methylene blue dye

In this study, a novel approach for the removal of methylene blue (MB) dye is effectively illustrated by using biomass based composite adsorbent. The investigation employed areca nut husk (AH) to produce graphene oxide (GO) by a single step calcination method. Thereafter, AH-GO was incorporated by using ternary metal oxide (TMO) via hydrothermal treatment. The developed AH-GO@MnO-NiO-ZnO composite was characterized by various analytical techniques, including FT-IR, XRD, FESEM, HRTEM, BET surface area and Raman spectroscopy which exhibited promising properties for dye adsorption. To study the adsorption efficiency of prepared composite, optimization experiments were performed for adsorbent dose, initial dye concentration and contact time. The optimized parameters during adsorption phenomenon were found to be 0.5g/L of dose, 20mg/L of initial concentration and 180min of time exhibiting removal efficacy of 93.05 ± 0.93%. Moreover, adsorption isotherm and kinetic models were analysed to explore the adsorption behaviour of AH-GO@MnO-NiO-ZnO towards MB dye. The adsorption isotherm and kinetic studies followed Langmuir isotherm model and pseudo-second-order (PSO) model respectively. AH-GO@MnO-NiO-ZnO has demonstrated a maximum adsorption capability of 127.06mg/g. These findings collectively underscore the potential of AH-based adsorbent as a viable, inexpensive, and environment friendly for the treatment of wastewater contaminated with MB dye.

Three-dimensional moisture transport fabric for enhanced moisture management in protective clothing

Effective moisture management within the microenvironment of protective clothing is crucial for maintaining garment performance and wearer comfort. The inherent properties of fabrics and the structural of protective garments often hinder the discharge of sweat to the external environment. Here, we present a novel 3D moisture transport fabric, engineered with gradient wetting properties along both the thickness and length dimensions. This fabric can transport moisture from the inner to the outer surface within approximately 5 s, achieving a maximum accumulative one-way transport capability of 1189.1 in the thickness direction. Additionally, by further directing moisture along the constructed wetting gradient on the fabric's outer surface, the moisture diffusion distance in the gradient direction was up to 2.6 times greater than in other directions. This approach will enhance moisture transport and management within protective clothing and can be further extended to the development of materials for oil-water separation, wound dressings, flexible microfluidics, and fuel cell membranes.

Dual redox centers in MnCo2O4 nanorod cathode for highly efficient capacitive deionization

Capacitive deionization (CDI) technology via faradic electrodes with active redox pairs has achieved tremendous success in desalination. However, the inner collaborative mechanisms of multi-redox centers in electrodes are rarely deep-analyzed. Thus, this work intensively investigated the inner enhanced mechanisms of multi-redox centers, starting from the dual-redox-based MnCo2O4 nanorod (MCO-NR) cathode in capacitive desalination. The electrochemical tests indicated a surface capacitive ratio of MCO-NR as high as 86 % when the scan rate was 100 mV s−1. Multi-dimensional CDI tests demonstrated that the highest capacity of MCO-NR could reach 61.78 mg g−1, with four theory models elaborating the electrosorption kinetics and maximum desalination capability. The refined ex-situ XPS measurements, carefully designed comparative experiments, and DFT calculations were used to analyze the Na+ (de)intercalation characteristics, the inner enhanced electrosorption mechanisms of dual redox centers, and the effects that the Mn redox center exerts on the MnCo2O4 structure. These results showed the superiority of dual- or multi-redox-center-based faradic capacitive desalination, providing a new perspective for designing high-property faradic electrode materials.

Changes in strength performance of highly trained athletes after COVID-19

Introduction This study aimed to explore the impact of COVID-19 on strength performance in highly trained athletes. Method A force plate was employed to measure squat jump height (SJH), counter-movement jump height (CMJH), and drop jump reactive strength index (DJRSI) in 27 highly trained athletes before infection, and at one week, two weeks, and four weeks post-recovery. Additionally, an Isometric Mid-thigh Pull (IMTP) test was conducted to record maximum isometric strength (MIS) and the rate of force development of the initial phase (RFD 0–50; RFD 0–100). Repeated measures analysis of variance was utilized to compare variations in these indicators across different time points. Results One week post-recovery, SJH (-7.71%, P = 0.005), CMJH (-9.08%, P < 0.001), DJRSI (-28.88%, P < 0.001), MIS (-18.95%, P < 0.001), RFD 0–50 (-64.98%, P < 0.001), and RFD 0–100 (-53.65%, P < 0.001) were significantly lower than pre-infection levels. Four weeks post-recovery, SJH (-2.08%, P = 0.236), CMJH (-3.28%, P = 0.277), and MIS (-3.32%, P = 0.174) did not differ significantly from pre-infection levels. However, DJRSI (-11.24%, P = 0.013), RFD 0–50 (-31.37%, P = 0.002), and RFD 0–100 (-18.99%, P = 0.001) remained significantly lower than pre-infection levels. Conclusion After COVID-19, highly trained athletes exhibited a significant reduction in maximum strength, explosive strength, reactive strength, and initial phase force generation capability. By four weeks post-recovery, their maximum and explosive strength had returned to near pre-infection levels, yet their reactive strength and initial phase force generation capability remained significantly impaired.

A Design Proposal Using Coherently Radiating Periodic Structures (CORPSs) for 2-D Phased Arrays of Limited Scanning

New configurations of 2-D phased arrays are proposed in this paper for reducing the number of phase shifters. This design methodology is based on the use of a novel coherently radiating periodic structures (CORPSs) block for 2-D phased arrays. Two new antenna systems for 2-D phased arrays are studied and analyzed utilizing the CORPSs blocks of four inputs and nine outputs. These CORPSs feeding blocks are applied in a smart way to feed the planar antenna arrays by generating the required phase plane and reducing the number of control ports. Interesting results are provided based on the experimental measurements and full-wave simulations. These results illustrate a great reduction of the active devices (phase shifters), providing a good design compromise in terms of the scanning range and side lobe level performance. Furthermore, the provided results illustrate a maximum reduction capability in the number of phase shifters of 81%, considering a scanning range of ±30° in azimuth and ±30° in elevation. A raised cosine distribution is applied to reach side lobe levels of −19 dB for ±18° and −17 dB for ±30° in elevation. These benefits could be of interest to designers of phased antenna systems.

Novel utilization exploration for the dephosphorization waste of Ca–modified biochar: enhanced removal of heavy metal ions from water

Phosphorus-modified biochar has been proven to enhance the precipitation and complexation of heavy metal ions from wastewater. However, the current modification methods require large amounts of exogenous P and have high energy consumption. Hence, this study proposes and analyzes a strategy integrating biochar production, phosphorus wastewater treatment, dephosphorization waste recovery, and heavy metal removal. “BC-Ca-P” was derived from Ca-modified biochar after phosphorus wastewater treatment. The adsorption of Pb(II) by BC-Ca-P followed the Langmuir isotherm and pseudo–second–order kinetic models. The maximum adsorption capability of 361.20 mg·g−1 at pH 5.0 for 2 h was markedly greater than that of external phosphorous-modified biochar. The adsorption mechanisms were dominated by chemical precipitation and complexation. Furthermore, density functional theory calculations indicated that oxygen-containing functional groups (P-O and C-O) contributed the most to the efficient adsorption of Pb(II) onto BC-Ca-P. To explore its practical feasibility, the adsorption performance of BC-Ca-P recovered from an actual environment was evaluated. The continuous-flow adsorption behavior was investigated and well-fitted utilizing the Thomas and Yoon–Nelson models. There was a negligible P leakage risk of BC-Ca-P during heavy metal treatment. This study describes a novel and sustainable method to utilize dephosphorization waste for heavy metal removal.Graphical

Can Your Leadership Increase Mine? Enabling IT Self-Leadership Through Transformational IT Leadership

Despite substantial investments by companies in technology projects, these resources are often not utilized to their maximum capability. People can enhance their use of technology by taking leadership in their IT use, i.e., by exhibiting IT self-leadership. This way, they may contribute to applying technology in ways that boost the innovativeness of their team. Therefore, the more IT self-leadership employees exhibit, the better the IT-utilization of the organization is. This study investigates the connection between the team leaders’ transformational IT leadership and team members’ IT self-leadership. Findings from diverse European teams in various industries indicate a positive relationship between the two.

Porous Spindle-Knot Fiber by Fiber-Microfluidic Phase Separation for Water Collection and Nanopatterning.

Porous spindle-knot structures have been found in many creatures, such as spider silk and the root of the soybean plant, which show interesting functions such as droplet collection or biotransformation. However, continuous fabrication of precisely controlled porous spindle-knots presents a big challenge, particularly in striking a balance among good structural controllability, low-cost, and functions. Here, we propose a concept of a fiber-microfluidics phase separation (FMF-PS) strategy to address the above challenge. This FMF-PS combines the advantages of a microchannel regulated Rayleigh instability of polymer solution coated onto a fiber with the nonsolvent-induced phase separation of the polymer solution, which enables continuous and cost-effective production of porous spindle-knot fiber (PSKF) with well-controlled size and porous structures. The critical factors controlling the geometry and the porous structures of the spindle-knot by FMF-PS have been systematically investigated. For applications, the PSKF exhibited faster water droplet nucleation, growth, and maximum water collection capability, compared to the control samples, as revealed by in situ water collection growth curves. Furthermore, high-level fabrics of the PSKFs, including a two-dimensional network and three-dimensional architecture, have been demonstrated for both large-scale water collection and art performance. Finally, the PSKF is demonstrated as a programmable building block for surface nanopatterning.

Optimization of Joint Space Trajectories for Assistive Lower Limb Exoskeleton Robots: Real-Time and Flexible Gait Patterns

This research focuses on designing a real-time, flexible gait planner for lower limb exoskeleton robots to assist patients with lower limb disabilities. Given the dynamic nature of gait parameters, which vary according to ground conditions and user intent, the challenge lies in developing a gait planner capable of adapting to these changes in real-time. To avoid planning complications in the cartesian space and to comply with the speed constraints of joint motors, this paper proposes planning in joint space. Furthermore, the approach also considers the maximum speed capabilities of the joint motors, aiming to generate an executable gait pattern and simultaneously enhance the robot’s walking speed by determining the minimum time required for implementation. The introduced gait planner optimizes joint trajectories for minimal angular acceleration. To provide flexibility, generalized boundary conditions suitable for different scenarios are defined. The effectiveness of the proposed planner is validated through comprehensive performance analysis, simulations, and successful implementation trials on the Exoped® robot in various scenarios.

A new approach to instantaneous power based control of DFIG using active disturbance rejection control

This paper presents the design and control of a wind energy converter system that uses a doubly fed induction generator. It introduces a model that incorporates instantaneous active and reactive power as state variables to represent both the stator and rotor sides of the doubly fed induction generator. Subsequently, a linear active disturbance rejection-based control regulator is proposed for the control loops. The parameters of the linear active disturbance rejection controllers (ADRC) are adjusted by two methods: the single parameter tuning approach and the genetic algorithm (GA) method. The performance of the suggested controller is ultimately compared with a tuned proportional-integral (PI) control regulator in the MATLAB environment. In order to examine the performance of the system, various test scenarios are taken into account. These scenarios include different percentages of load change in both sub-synchronous and super-synchronous modes of operation, faults with different fault periods are considered in both modes of operation. The conventional PI controller-based approach requires 35 control cycles to reach steady state under load change conditions and 50 control cycles under symmetrical fault conditions, regardless of whether the system is operating in sub synchronous or super synchronous mode. The single parameter-based tuned ADRC approach only requires 15 control cycles for load change and 20 control cycles for symmetrical fault scenarios. In contrast, for both the load change and symmetrical fault scenarios, the ADRC with GA-based parameter tuning reaches steady state in just 5 control cycles. Furthermore, a case involving wind speed variation is presented to demonstrate the maximum power point tracking capability of the proposed control structure. Similarly, for the robustness test of the control regulator, variations in resistance and inductance are introduced to observe their impact on the response of the control regulators. Finally, a real-time hardware in loop setup is presented to validate the control strategy during the load change in the sub-synchronous mode of operation of the doubly fed induction generator.

Effect of number of triggers and shape of crash box on energy absorption during experimental collision

The capacity of passenger car crash boxes to absorb energy during crashes has been the subject of extensive research, which started with the creation of multiple crash box models, changes in crash box filling, and the inclusion of crash box triggers. On the other hand, no research has been done on the combination of axle trigger holes, nine-cell columns, and crash box models. The results of the experiment on the energy-absorbing capacity of AA6061-T4 crash box specimens under compressive loads are presented in this paper. The compression tests were conducted on a Universal Testing Machine with a maximum force capability of 1000 kN and a speed capability of 5 mm/s. Three models are used in crash box modeling. A cross-section of the model with a round hole-shaped trigger variation is included in these three versions. It is established that the hexagonal Frusta type with two holes absorbs the highest energy at 33.30 kJ, and has a displacement of 4.12 mm and a maximum force of 348.5 kN. The energy absorption capacity of the crash box was found to be increased by combining frusta versions of the hexagon model with two holes and nine-cell column filling.

Numerical investigations on the performance of coupled NCL based passive heat removal system of an IPHWR

Passive heat removal systems (PHRS) are indispensable additional safety features in nuclear reactors to deal with station blackout (SBO) conditions. These systems are based on coupled natural circulation loops (C-NCL) connected in series configuration. Further, these system's design, operating conditions, working fluid, heat removal capacity, etc., are specific to the reactor type. In the present work, the operational performance of such first of a kind PHRS of 700 MWe Indian pressurized heavy water reactor (IPHWR) is investigated. For this purpose, a coupled two-phase NCL code is developed, validated and employed. This PHRS consists of two NCLs connected in HHVC-VHVC (horizontal heater and vertical cooler - vertical heater and vertical cooler) configuration. In this study, initially, the full power reactor thermal-hydraulic conditions are established, subsequently, the performance of the PHRS under SBO is investigated. The analyses demonstrated that the system is adequate to effectively eradicate the decay heat by establishing single and two-phase natural circulation (NC) flows of ∼4.5 % and ∼5.6 % of rated conditions in primary and secondary transport loops, respectively. The maximum PHRS capability is predicted to be ∼72 MWth which is more than 3 % of full power. The transients of flow, pressure, energy transfer and heat sink thermal conditions are analyzed when the system changes from forced to NC. Further, the influence of system conditions such as loop diameter, loop height, sink volume, sink temperature and heat exchanger area on PHRS performance was predicted and the changes in system parameters were analyzed. The vital parameters influencing the PHRS performance are identified based on sensitivity analyses. This investigation provides significant insight into the flow and heat transfer characteristics of two-phase and coupled NCLs in the PHRS.

Removal of crocein orange G from water solutions by trimetallic nanoparticles [Co/Cu/M (M=Ni, Zn)] prepared by chemical reduction method

Co-Cu-Ni and Co-Cu-Zn trimetallic nanoparticles (NPs) were prepared by chemical reduction method which were then used as adsorbent to remove Crocein Orange G dye from solution. The elemental composition of the fabricated NPs was determined by EDX analysis, surface morphology was assessed by SEM, and its crystalline nature was confirmed by XRD analysis. The functional groups on nanoparticles were confirmed by FT-IR analysis. The optimum dosage was found to be 0.01 g. Langmuir model as well as linear pseudo 2nd order kinetics models best explained the obtained data. The maximum adsorption capabilities were found to be around 497.618 mg/g and 683.093 mg/g, respectively for Co-Cu-Ni and Co-Cu-Zn trimetallic NPs. The adsorption process was exothermic, as evidenced from the positive ΔH° values. The negative values of ΔG° at the corresponding temperatures support the spontaneous nature of the adsorption processes. The positive entropy changes (ΔS°) suggested that there is more disorderness at the interface between the solid and the solution during the adsorption. The fabricated trimetallic nanoparticles have effectively adsorbed Crocein Orange G, which may be considered as an attractive option in wastewater treatment and environmental remediation applications due to diversity of metal ions on surface offering differential attractive forces for pollutant.

A low dropout regulator design with 20.4 μA quiescent current and high power supply rejection

This paper presents a novel low dropout (LDO) regulator distinguished by its high power supply rejection (PSR) and low quiescent current. A capacitive feed-forward ripple cancellation (CFFRC) technique is introduced to effectively cancel power supply noise while simultaneously minimizing quiescent current. Additionally, the design incorporates feed-forward capacitors and back-to-back pseudo-resistors biasing to achieve reduced power consumption. Furthermore, the integration of negative feedback super source follower and Miller compensation techniques enhances the stability of the LDO. Fabricated using 180 nm CMOS technology, the LDO exhibits a quiescent current consumption of 20.4 μA. Experimental results demonstrate a maximal improvement of −41.55 dB in PSR compared to an LDO lacking these enhancements, with a maximum load current capability of 120 mA.

Day/Night Power Generator Station: A New Power Generation Approach for Lunar and Martian Space Exploration

In the not-too-distant future, humans will return to the Moon and step foot for the first time on Mars. Eventually, humanity will colonize these celestial bodies, where living and working will be commonplace. Energy is fundamental to all life. The energy that people use to sustain themselves on Earth, and in particular on these other worlds, is the integrated, safe production of electrical power, day and night. This paper proposes a radically new solution to this problem: Solar Tracking by day and a Solar Rechargeable Calcium Oxide Chemical Thermoelectric Reactor by night. Called the “Robotic End Effector for Lunar and Martian Geological Exploration of Space” (REEGES) Day/Night Power Generator Station, this form of thermoelectric power generation is mathematically modeled, simulation is performed, and a concept model design is demonstrated in this paper. The results of the presented simulation show the maximum total system output capability is 9.89 V, 6.66 A, and 65.9 W, with an operating time of up to 12 h, through a scalable design. This research provides instructions to the Space Research Community on a complete and novel development methodology for creating fully customized, configurable, safe, and reliable solar/thermoelectric day/night power generators, specifically meant for use on the Moon and Mars, using the Proportional-Integral-Derivative++ (PID++) Humanoid Motion Control Algorithm for its operation on a computationally lightweight microcontroller.

Evidence for particle acceleration approaching PeV energies in the W51 complex

The γ-ray emission from the W51 complex is widely acknowledged to be attributed to the interaction between the cosmic rays (CRs) accelerated by the shock of supernova remnant (SNR) W51C and the dense molecular clouds in the adjacent star-forming region, W51B. However, the maximum acceleration capability of W51C for CRs remains elusive. Based on observations conducted with the Large High Altitude Air Shower Observatory (LHAASO), we report a significant detection of γ rays emanating from the W51 complex, with energies from 2 to 200 TeV. The LHAASO measurements, for the first time, extend the γ-ray emission from the W51 complex beyond 100 TeV and reveal a significant spectrum bending at tens of TeV. By combining the “π0-decay bump” featured data from Fermi-LAT, the broadband γ-ray spectrum of the W51 region can be well-characterized by a simple pp-collision model. The observed spectral bending feature suggests an exponential cutoff at ∼400 TeV or a power-law break at ∼200 TeV in the CR proton spectrum, most likely providing the first evidence of SNRs serving as CR accelerators approaching the PeV regime. Additionally, two young star clusters within W51B could also be theoretically viable to produce the most energetic γ rays observed by LHAASO. Our findings strongly support the presence of extreme CR accelerators within the W51 complex and provide new insights into the origin of Galactic CRs.

Spectral codes of real symmetric operators for error correction

In this paper, we introduce a novel class of real number codes termed as [Formula: see text]-spectral codes, derived from real symmetric operators. Our focus is on addressing the challenges associated with error correction in communication systems utilizing real number codes. Our study initiates with a meticulous definition and analysis of the fundamental properties of [Formula: see text]-spectral codes. These properties serve as the foundation for comprehending the distinctive characteristics that [Formula: see text]-spectral codes offer, ensuring the integrity and reliability of transmitted data. Our exploration extends to the construction of maximum distance separable (MDS) [Formula: see text]-spectral codes, which boast the maximum error correction capability. As a culmination of our research, we present an efficient decoding technique tailored for [Formula: see text]-spectral codes. Leveraging an MDS [Formula: see text]-spectral code and our decoding technique, we achieve optimal error correction and ensure good numerical stability. This innovative approach opens new avenues for enhancing the performance of real-number codes in practical applications.

Tensile strength optimisation in AA2014 aluminum alloy joints via friction stir welding: a rivet-free approach examining materials flow behaviour

ABSTRACT Steel rivets are alternative materials for connecting materials for structural fabrication industry. The use of rivets may significantly increase the structure weight, impacting its overall performance. Additionally, there is a risk of inducing corrosion at the interface due to galvanic coupling. Therefore, careful consideration of material choices and potential consequences is necessary during the design and fabrication processes. When joining dissimilar alloys, manufacturers and designers face numerous challenges with conventional fusion welding techniques. Friction stir welding is effective at joining materials without reaching their melting points; instead, it relies on severe plastic deformation and recrystallization to create a welded joint. Proper selection of the tool and process parameters is crucial for achieving a sound weld result. The results from experimental investigations highlight the significance of plastic deformation, material flow, and recrystallization as influential factors on joint strength. This finding suggested that FSW is an ideal joining process for high-strength alloys. Although friction stir welding is a suitable alternative to permanent joints, such as rivets, notably, the experimental findings reveal that friction stir welding of both but and lap joints yields maximum load-carrying capabilities of 50.5 and 51.2 kN, respectively, emphasising the efficacy of the method in structural applications